Randomization of current in a power converter

ABSTRACT

A method of randomizing inductor current in at least one of a plurality of parallel coupled peak valley current-controlled power converters may include comparing the inductor current to a threshold to generate a comparison signal, delaying the comparison signal by a plurality of delay amounts to generate a plurality of delayed versions of the comparison signal, and randomly selecting one of the plurality of delayed versions of the comparison signal for controlling the inductor current during one or both of a charging state and a transfer state of the at least one of the plurality of parallel coupled peak/valley current-controlled power converters.

RELATED APPLICATION

The present disclosure claims priority to U.S. Provisional PatentApplication Ser. No. 63/027,596 filed May 20, 2020, U.S. ProvisionalPatent Application Ser. No. 63/027,555 filed May 20, 2020, U.S.Provisional Patent Application Ser. No. 63/027,586 filed May 20, 2020,U.S. Provisional Patent Application Ser. No. 63/027,533 filed May 20,2020, and U.S. Provisional Patent Application Ser. No. 63/027,547 filedMay 20, 2020, all of which are incorporated by reference herein in theirentireties.

FIELD OF DISCLOSURE

The present disclosure relates in general to circuits for electronicdevices, including without limitation personal audio devices such aswireless telephones and media players, and more specifically, toprediction of a load current and a control current in a power converterusing output voltage thresholds.

BACKGROUND

Personal audio devices, including wireless telephones, such asmobile/cellular telephones, cordless telephones, mp3 players, and otherconsumer audio devices, are in widespread use. Such personal audiodevices may include circuitry for driving a pair of headphones or one ormore speakers. Such circuitry often includes a speaker driver includinga power amplifier for driving an audio output signal to headphones orspeakers. Oftentimes, a power converter may be used to provide a supplyvoltage to a power amplifier in order to amplify a signal driven tospeakers, headphones, or other transducers. A switching power converteris a type of electronic circuit that converts a source of power from onedirect current (DC) voltage level to another DC voltage level. Examplesof such switching DC-DC converters include but are not limited to aboost converter, a buck converter, a buck-boost converter, an invertingbuck-boost converter, and other types of switching DC-DC converters.Thus, using a power converter, a DC voltage such as that provided by abattery may be converted to another DC voltage used to power the poweramplifier.

A power converter may be used to provide supply voltage rails to one ormore components in a device. Accordingly, it may be desirable toregulate an output voltage of a power converter with minimal ripple inthe presence of a time-varying current and power load.

SUMMARY

In accordance with the teachings of the present disclosure, one or moredisadvantages and problems associated with existing approaches toregulating an output voltage of a power converter may be reduced oreliminated.

In accordance with embodiments of the present disclosure, a system forcontrolling a current in a power converter may include an outer controlloop configured to use an outer set of output voltage thresholds for anoutput voltage generated by the power converter in order to providehysteretic control of the current, an inner control loop configured touse an inner set of output voltage thresholds for the output voltage inorder to provide continuous control of the current, the inner controlloop further configured to measure a time duration required for theoutput voltage to cross a single pair of two output voltage thresholdsof the inner set of output voltage thresholds in order to determine aninput-referred estimate of a current load of the power converter and seta peak current threshold and a valley current threshold for the currentbased on the input-referred estimate of the current load.

In accordance with these and other embodiments of the presentdisclosure, a system may include an inductive power converter configuredto receive an input voltage and generate an output voltage and a switchcontroller for controlling switching of the inductive power converter todefine a charging state and a transfer state of the inductive powerconverter, wherein the switch controller comprises a plurality ofcomparators, each comparator having a respective reference voltage towhich the output voltage is compared, and wherein the plurality ofcomparators are used for controlling the inductive power converter inone or both of a hysteretic control mode and a continuous control mode.

In accordance with these and other embodiments of the presentdisclosure, a method for controlling a current in a power converter mayinclude applying an outer control loop configured to use an outer set ofoutput voltage thresholds for an output voltage generated by the powerconverter in order to provide hysteretic control of the current andapplying an inner control loop configured to use an inner set of outputvoltage thresholds for the output voltage in order to provide continuouscontrol of the current, the inner control loop further configured tomeasure a time duration required for the output voltage to cross asingle pair of two output voltage thresholds of the inner set of outputvoltage thresholds in order to determine an input-referred estimate of acurrent load of the power converter and set a peak current threshold anda valley current threshold for the current based on the input-referredestimate of the current load.

In accordance with these and other embodiments of the presentdisclosure, a method may include controlling switching of an inductivepower converter to define a charging state and a transfer state of theinductive power converter, wherein the power converter is configured toreceive an input voltage and generate an output voltage and whereincontrolling comprises using a plurality of comparators for controllingthe inductive power converter in one or both of a hysteretic controlmode and a continuous control mode, each comparator having a respectivereference voltage to which the output voltage is compared.

In accordance with these and other embodiments of the presentdisclosure, a system for controlling a current in a power converterconfigured to generate an output voltage may include a control loophaving a plurality of comparators, each comparator having a respectivereference voltage to which the output voltage is compared, a digitalcontroller configured to calculate one or more pre-seeded controlparameters for the current, and an analog state machine configured to,based on outputs of the plurality of comparators, select controlparameters for controlling the current. The control parameters may beselected from the pre-seeded control parameters, control parameters forcontrolling the current to have a magnitude of zero, and controlparameters for controlling the current to have a maximum magnitude.

In accordance with these and other embodiments of the presentdisclosure, a method for controlling a current in a power converterconfigured to generate an output voltage may include using a controlloop having a plurality of comparators, each comparator having arespective reference voltage to which the output voltage is compared, adigital controller configured to calculate one or more pre-seededcontrol parameters for the current, and an analog state machineconfigured to, based on outputs of the plurality of comparators, selectcontrol parameters for controlling the current. The control parametersmay be selected from the pre-seeded control parameters, controlparameters for controlling the current to have a magnitude of zero, andcontrol parameters for controlling the current to have a maximummagnitude.

In accordance with these and other embodiments of the presentdisclosure, a method of randomizing inductor current in at least one ofa plurality of parallel coupled peak/valley current-controlled powerconverters may include comparing the inductor current to a threshold togenerate a comparison signal, delaying the comparison signal by aplurality of delay amounts to generate a plurality of delayed versionsof the comparison signal, and randomly selecting one of the plurality ofdelayed versions of the comparison signal for controlling the inductorcurrent during one or both of a charging state and a transfer state ofthe at least one of the plurality of parallel coupled peak/valleycurrent-controlled power converters.

In accordance with these and other embodiments of the presentdisclosure, a method of randomizing inductor current in at least one ofa plurality of parallel coupled peak/valley current-controlled powerconverters may include randomly selecting an offset current parameter,adding the offset current parameter to a reference current parameter togenerate a modified reference current parameter, and comparing theinductor current to the modified reference current parameter to controlthe inductor current during one or both of a charging state and atransfer state of the at least one of the plurality of parallel coupledpeak/valley current-controlled power converters.

In accordance with these and other embodiments of the presentdisclosure, a system of randomizing inductor current in at least one ofa plurality of parallel coupled peak/valley current-controlled powerconverters may include a comparator configured to compare the inductorcurrent to a threshold to generate a comparison signal, delay elementsconfigured to delay the comparison signal by a plurality of delayamounts to generate a plurality of delayed versions of the comparisonsignal, and selection logic configured to randomly select one of theplurality of delayed versions of the comparison signal for controllingthe inductor current during one or both of a charging state and atransfer state of the at least one of the plurality of parallel coupledpeak/valley current-controlled power converters.

In accordance with these and other embodiments of the presentdisclosure, a system of randomizing inductor current in at least one ofa plurality of parallel coupled peak/valley current-controlled powerconverters may include selection logic configured to randomly selectingan offset current parameter, a combiner configured to add the offsetcurrent parameter to a reference current parameter to generate amodified reference current parameter, and a comparator configured tocompare the inductor current to the modified reference current parameterto control the inductor current during one or both of a charging stateand a transfer state of the at least one of the plurality of parallelcoupled peak/valley current-controlled power converters.

In accordance with these and other embodiments of the presentdisclosure, a system may include a power converter configured to receivean input voltage and generate an output voltage and a controllerconfigured to control operation of the power converter based on acomparison of the output voltage with at least one output voltagethreshold and set the at least one output voltage threshold based on theinput voltage.

In accordance with these and other embodiments of the presentdisclosure, a method may include controlling operation of a powerconverter configured to receive an input voltage and generate an outputvoltage, such controlling based on a comparison of the output voltagewith at least one output voltage threshold and setting the at least oneoutput voltage threshold based on the input voltage.

In accordance with these and other embodiments of the presentdisclosure, a system may include a power converter configured to receivean input voltage and generate an output voltage and a controllerconfigured to control operation of the power converter based on acomparison of a current associated with the power converter to athreshold current and control the threshold current as a function of theinput voltage.

In accordance with these and other embodiments of the presentdisclosure, a method may include controlling operation of a powerconverter configured to receive an input voltage and generate an outputvoltage, such controlling based on a comparison of a current associatedwith the power converter to a threshold current and controlling thethreshold current as a function of the input voltage.

Technical advantages of the present disclosure may be readily apparentto one skilled in the art from the figures, description and claimsincluded herein. The objects and advantages of the embodiments will berealized and achieved at least by the elements, features, andcombinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description andthe following detailed description are examples and explanatory and arenot restrictive of the claims set forth in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 illustrates an example mobile device, in accordance withembodiments of the present disclosure;

FIG. 2 illustrates a block diagram of selected components internal to amobile device, in accordance with embodiments of the present disclosure;

FIG. 3A illustrates a block diagram of selected components of an exampleboost converter with multiple modes of operation depicting operation ina bypass mode, in accordance with embodiments of the present disclosure;

FIG. 3B illustrates a block diagram of selected components of an exampleboost converter with multiple modes of operation depicting operation ina boost active mode, in accordance with embodiments of the presentdisclosure;

FIG. 3C illustrates a block diagram of selected components of an exampleboost converter with multiple modes of operation depicting operation ina boost inactive mode, in accordance with embodiments of the presentdisclosure;

FIG. 4 illustrates a graph of inductor current through a phase of aboost converter and a control signal of switches of the phase versustime, in accordance with embodiments of the present disclosure;

FIG. 5 illustrates a block diagram of selected components of an examplecontrol circuit for a boost converter, in accordance with embodiments ofthe present disclosure;

FIG. 6 illustrates an example graph of a supply voltage generated by theboost converter of FIGS. 3A-3C versus time, in accordance with thepresent disclosure;

FIG. 7 illustrates a waveform of a supply voltage generated by a powerconverter over a period of time and a waveform of an inductor currentwithin the power converter over the same period of time, in accordancewith the present disclosure;

FIG. 8 illustrates a block diagram of selected components of an outercontrol loop subsystem of the current controller shown in FIG. 5 , inaccordance with embodiments of the present disclosure;

FIG. 9 illustrates example waveforms depicting an example of outer loopcontrol for a boost converter, in accordance with embodiments of thepresent disclosure;

FIG. 10 illustrates a block diagram of selected components of an innercontrol loop subsystem of the current controller shown in FIG. 5 , inaccordance with embodiments of the present disclosure;

FIG. 11 illustrates example waveforms depicting an example of inner loopcontrol for a boost converter, in accordance with embodiments of thepresent disclosure;

FIG. 12 illustrates example waveforms depicting an example of inner loopcontrol for a boost converter in light-load scenarios, in accordancewith embodiments of the present disclosure;

FIG. 13 illustrates a block diagram of selected components of anotherexample control circuit for a boost converter, in accordance withembodiments of the present disclosure;

FIG. 14 illustrates a block diagram of selected components of an innercontrol loop subsystem of the current controller shown in FIG. 13 , inaccordance with embodiments of the present disclosure;

FIG. 15 illustrates a block diagram of selected components of an outercontrol loop subsystem of the current controller shown in FIG. 13 , inaccordance with embodiments of the present disclosure;

FIG. 16 illustrates a block diagram of selected components of an examplepeak/valley controller, in accordance with embodiments of the presentdisclosure;

FIGS. 17A-17C illustrate graphs of various example waveforms for batterycurrent, boost converter inductor currents, and boost converter controlsignals versus time, in accordance with embodiments of the presentdisclosure;

FIG. 18 illustrates a block diagram of selected components of an examplepeak/valley controller with circuitry for performing time-domain phaserandomization of inductor currents in a boost converter, in accordancewith embodiments of the present disclosure;

FIG. 19 illustrates a graph of example waveforms for boost converterinductor currents with time-domain phase randomization, in accordancewith embodiments of the present disclosure;

FIG. 20 illustrates a block diagram of selected components of an examplepeak/valley controller with circuitry for performing level-domain phaserandomization of inductor currents in a boost converter, in accordancewith embodiments of the present disclosure;

FIG. 21 illustrates a graph of example waveforms for boost converterinductor currents with level-domain phase randomization, in accordancewith embodiments of the present disclosure;

FIG. 22 illustrates a graph of various example waveforms for a loadcurrent delivered from a boost converter, a supply voltage generated bythe boost converter, and inductor currents for phases of the boostconverter, in accordance with embodiments of the present disclosure;

FIG. 23 illustrates a graph of various example waveforms for a loadcurrent delivered from a boost converter, threshold voltages forregulating a supply voltage generated by the boost converter, the supplyvoltage, and a sensed voltage at the input of the boost converter, inaccordance with embodiments of the present disclosure;

FIG. 24 illustrates selected components of a control subsystem providingfor voltage-domain hysteretic control of threshold voltages forregulating a supply voltage generated by the boost converter, inaccordance with embodiments of the present disclosure;

FIG. 25 illustrates a graph of various example waveforms for a sensedvoltage at an input of a boost converter and a flag for togglingthreshold voltages for regulating a supply voltage generated by theboost converter, in accordance with embodiments of the presentdisclosure;

FIG. 26 illustrates selected components of a control subsystem providingfor time-domain hysteretic control of threshold voltages for regulatinga supply voltage generated by the boost converter, in accordance withembodiments of the present disclosure;

FIG. 27 illustrates a graph of various example waveforms for a sensedvoltage at an input of a boost converter and a flag for togglingthreshold voltages for regulating a supply voltage generated by theboost converter, in accordance with embodiments of the presentdisclosure;

FIG. 28 illustrates selected components of a control subsystem providingfor control of threshold voltages for regulating a supply voltagegenerated by the boost converter, in accordance with embodiments of thepresent disclosure;

FIG. 29 illustrates a graph of various example waveforms for a sensedvoltage at an input of a boost converter, a flag for toggling thresholdvoltages for regulating a supply voltage generated by the boostconverter, and the supply voltage, in accordance with embodiments of thepresent disclosure;

FIG. 30 illustrates a graph of various example waveforms for a supplyvoltage generated by a boost converter and inductor currents for phasesof the boost converter, in accordance with embodiments of the presentdisclosure; and

FIG. 31 illustrates a graph of various example waveforms for a supplyvoltage generated by a boost converter, inductor currents for phases ofthe boost converter, and a sensed voltage at an input of the boostconverter, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates an example mobile device 1, in accordance withembodiments of the present disclosure. FIG. 1 depicts mobile device 1coupled to a headset 3 in the form of a pair of earbud speakers 8A and8B. Headset 3 depicted in FIG. 1 is merely an example, and it isunderstood that mobile device 1 may be used in connection with a varietyof audio transducers, including without limitation, headphones, earbuds,in-ear earphones, and external speakers. A plug 4 may provide forconnection of headset 3 to an electrical terminal of mobile device 1.Mobile device 1 may provide a display to a user and receive user inputusing a touch screen 2, or alternatively, a standard liquid crystaldisplay (LCD) may be combined with various buttons, sliders, and/ordials disposed on the face and/or sides of mobile device 1.

FIG. 2 illustrates a block diagram of selected components integral tomobile device 1, in accordance with embodiments of the presentdisclosure. As shown in FIG. 2 , mobile device 1 may include a boostconverter 20 configured to boost a battery voltage V_(BAT) to generate asupply voltage V_(SUPPLY) to a plurality of down stream components 18 ofmobile device 1. Downstream components 18 of mobile device 1 may includeany suitable functional circuits or devices of mobile device 1,including without limitation processors, audio coder/decoders,amplifiers, display devices, etc. As shown in FIG. 2 , mobile device 1may also include a battery charger 16 for recharging battery 22.

In some embodiments of mobile device 1, boost converter 20 and batterycharger 16 may comprise the only components of mobile device 1electrically coupled to battery 22, and boost converter 20 mayelectrically interface between battery 22 and all downstream componentsof mobile device 1. However, in other embodiments of mobile device 1,some downstream components 18 may electrically couple directly tobattery 22.

FIG. 3A illustrates a block diagram of selected components of an exampleboost converter 20 with multiple modes of operation depicting operationin a bypass mode, in accordance with embodiments of the presentdisclosure. As shown in FIG. 3A, boost converter 20 may include abattery 22, a plurality of inductive boost phases 24, a sense capacitor26, a sense resistor 28, a bypass switch 30, and a control circuit 40.As shown in FIG. 3A, each inductive boost phase 24 may include a powerinductor 32, a charge switch 34 a rectification switch 36, and outputcapacitor 38.

Although FIGS. 3A-3C depict boost converter 20 having three inductiveboost phases 24, embodiments of boost converter 20 may have any suitablenumber of inductive boost phases 24. In some embodiments, boostconverter 20 may comprise three or more inductive boost phases 24. Inother embodiments, boost converter 20 may comprise fewer than threephases (e.g., a single phase or two phases).

Boost converter 20 may operate in the bypass mode when supply voltageV_(SUPPLY) generated by boost converter 20 is greater than a thresholdminimum voltage V_(MIN). In some embodiments, such threshold minimumvoltage V_(MIN) may be a function of a monitored current (e.g., acurrent through sense resistor 28). In some embodiments, such thresholdminimum voltage V_(MIN) may be varied in accordance with variations inthe monitored current, in order to provide desired headroom fromcomponents supplied from supply voltage V_(SUPPLY). Control circuit 40may be configured to sense supply voltage V_(SUPPLY) and compare supplyvoltage V_(SUPPLY) to threshold minimum voltage V_(MIN). In the eventthat supply voltage V_(SUPPLY) and voltage VDD_SENSE across sensecapacitor 26 are greater than threshold minimum voltage V_(MIN), controlcircuit 40 may activate (e.g., enable, close, turn on) bypass switch 30and one or more rectification switches 36 and deactivate (e.g., disable,open, turn off) charge switches 34. In such bypass mode, the resistancesof rectification switches 36, power inductors 32, and bypass switch 30may combine to minimize a total effective resistance of a path betweenbattery 22 and supply voltage V_(SUPPLY).

FIG. 3B illustrates a block diagram of selected components of exampleboost converter 20 depicting operation in a boost active mode, inaccordance with embodiments of the present disclosure. Boost converter20 may operate in the boost active mode when supply voltage V_(SUPPLY)is insufficient to maintain supply voltage V_(SUPPLY) above thresholdminimum voltage V_(MIN). In the boost active mode, control circuit 40may deactivate (e.g., disable, open, turn off) bypass switch 30, andperiodically commutate charge switches 34 (e.g., during a charging stateof a phase 24) and rectification switches 36 (e.g., during a transferstate of a phase 24) of inductive boost phase 24 (as described ingreater detail below) by generating appropriate control signals P₁, P₁ ,P₂, P₂ , P₃, and P₃ , to deliver a current I_(BAT) and boost batteryvoltage V_(BAT) to a higher supply voltage V_(SUPPLY) in order toprovide a programmed (or servoed) desired current (e.g., averagecurrent) to the electrical node of supply voltage V_(SUPPLY), whilemaintaining supply voltage V_(SUPPLY) above threshold minimum voltageV_(MIN). In the boost active mode, voltage VDD_SENSE may fall belowthreshold minimum voltage V_(MIN). Further, in the boost active mode,boost converter 20 may operate as a single phase boost converter ormulti-phase boost converter.

In the boost active mode, control circuit 40 may operate boost converter20 by operating inductive boost phase 24 in a peak and valley detectoperation, as described in greater detail. The resulting switchingfrequency of charge switches 34 and rectification switches 36 ofinductive boost phase 24 may be determined by the sense voltageVDD_SENSE, supply voltage V_(SUPPLY), an inductance of power inductor32A, and a programmed ripple parameter (e.g., a configuration of atarget current ripple in power inductor 32A).

FIG. 3C illustrates a block diagram of selected components of boostconverter 20 depicting operation in a boost inactive mode, in accordancewith embodiments of the present disclosure. Boost converter 20 mayoperate in the boost inactive mode when supply voltage V_(SUPPLY)generated by boost converter 20 rises above a sum of threshold minimumvoltage V_(MIN) and a hysteresis voltage V_(HYST) and a sense voltageVDD_SENSE remains below threshold minimum voltage V_(MIN). In the boostinactive mode, control circuit 40 may deactivate (e.g., disable, open,turn off) bypass switch 30, charge switches 34, and rectificationswitches 36. Thus, when sense voltage VDD_SENSE remains below thresholdminimum voltage V_(MIN), control circuit 40 prevents boost converter 20from entering the bypass mode in order to not backpower battery 22 fromsupply voltage V_(SUPPLY). Further, if supply voltage V_(SUPPLY) shouldfall below threshold minimum voltage V_(MIN), control circuit 40 maycause boost converter 20 to again enter the boost active mode in orderto increase supply voltage V_(SUPPLY) to the sum of threshold minimumvoltage V_(MIN) and a hysteresis voltage V_(HYST).

As described above, when boost converter 20 operates in the boost activemode, control circuit 40 may provide hysteretic current control ofinductor currents I_(L1), I_(L2), and I_(L3) through power inductors32A, 32B, and 32C, respectively. FIG. 4 illustrates an example graph ofinductor current I_(L1) and control signal P₁ versus time, in accordancewith embodiments of the present disclosure. As shown in FIG. 4 , controlcircuit 40 may generate control signals P₁ and P₁ of phase 24A suchthat: (a) when inductor current I_(L1) falls below a valley currentthreshold I_(val1), control circuit 40 may activate charge switch 34Aand deactivate rectification switch 36A; and (b) when inductor currentI_(L1) increases above a peak current threshold I_(pk1), control circuit40 may deactivate charge switch 34A and activate rectification switch36A. Accordingly, control circuit 40 may provide hysteretic control ofinductor current I_(L1) such that inductor current I_(L1) varies betweenapproximately valley current threshold I_(val1) and approximately peakcurrent threshold I_(pk1), with inductor current I_(L1) having anaverage current I_(avg1) and a ripple current I_(ripple), such that:

${{I_{pk1} = {I_{{avg}1} + \frac{I_{ripple}}{2}}};{and}}{I_{{val}1} = {I_{{avg}1} - {\frac{I_{ripple}}{2}.}}}$Control circuit 40 may also generate control signals P₂, P₂ , P₃, and P₃of phases 24B and 24C to provide similar or identical control ofinductor currents I_(L2) and I_(L3).

FIG. 5 illustrates a block diagram of selected components of controlcircuit 40, in accordance with embodiments of the present disclosure. Asshown in FIG. 5 , control circuit 40 may comprise a plurality ofcomparators 42A, 42B, 42C, and 42D, each configured to compare supplyvoltage V_(SUPPLY) to a respective threshold voltage V₁, V₂, V₃, and V₄,and generate respective comparison signals C₁, C₂, C₃, and C₄.

Based on comparison signals C₁, C₂, C₃, and C₄, a load estimator 44 ofcontrol circuit 40 may implement an inner control loop to estimate aload seen at the output of boost converter 20, and based thereon,generate a target average current I_(avg) for battery current I_(BAT).The inner control loop may be said to provide continuous control ofinductor current I_(L). Further, based on comparison signals C₁, C₂, andC₄, and target average current I_(avg), a current controller 46 ofcontrol circuit 40 may implement an outer control loop. Both the innercontrol loop and outer control loop may be used to set valley currentthreshold I_(val), peak current threshold I_(pk), and a control signalENABLE for selectively enabling or disabling the boost active mode ofboost converter 20. In operation, the inner control loop may maximizeefficiency of boost converter 20 and minimize ripple on voltageV_(SUPPLY), while the outer control loop may bound a maximum ripple ofsupply voltage V_(SUPPLY). Based on valley current threshold I_(val) andpeak current threshold I_(pk), a peak/valley controller 48 of controlcircuit 40 may generate control signals for controlling power converter20.

FIG. 6 illustrates an example graph of supply voltage V_(SUPPLY) versustime, in accordance with the present disclosure. As shown in FIG. 6 ,threshold voltages V₁, V₂, V₃, and V₄ may divide the magnitude of supplyvoltage V_(SUPPLY) into five distinct regions A, B, C, D, and E. FIG. 6demonstrates how load estimator 44 may adjust target average currentI_(avg) in each of these five distinct regions A, B, C, D, and E.

Region A may be referred to as the MAX region. Is this region, supplyvoltage V_(SUPPLY) is below an undervoltage threshold represented bythreshold voltage V₁. Accordingly, in Region A, load estimator 44 mayset target average current I_(avg) to its maximum in order to causegeneration of as much inductor current I_(L) (e.g., I_(L1), I_(L2),I_(L3)) as possible in order to minimize droop of supply voltageV_(SUPPLY).

Region B may be referred to as the INCREMENT region. In this regionbetween threshold voltages V₁ and V₂, load estimator 44 may recursivelyincrement target average current I_(avg) in order to increase currentdelivered by boost converter 20 in order to increase supply voltageV_(SUPPLY). Load estimator 44 may increment target average currentI_(avg) using multiplicative recursion (e.g.,I_(avg(i+1))=I_(avg(i))×a₁, where a₁>1), additive recursion (e.g.,I_(avg(i+1))=I_(avg(i))+a₂, where a₂>0), or any other recursiveapproach.

Region C may be referred to as the MEASURE region, in which V_(SUPPLY)is between threshold voltages V₂ and V₃. In Region C, load estimator 44may measure a time in which supply voltage V_(SUPPLY) takes to crossthreshold voltages V₂ and V₃ and may update target average currentI_(avg) accordingly, as described in greater detail below.

Region D may be referred to as the DECREMENT region. In this regionbetween threshold voltages V₃ and V₄, load estimator 44 may recursivelydecrement target average current I_(avg) in order to decrease currentdelivered by boost converter 20 in order to decrease supply voltageV_(SUPPLY). Load estimator 44 may decrement target average currentI_(avg) using multiplicative recursion (e.g.,I_(avg(i+1))=I_(avg(i))×a₁, where a₁<1), additive recursion (e.g.,I_(avg(i+1))=I_(avg(i))+a₂, where a₂<0), or any other recursiveapproach.

Region E may be referred to as the HOLD region. In this region abovethreshold voltage V₄, load estimator 44 may hold or maintain the valueof decrement target average current I_(avg) (e.g.,I_(avg(i+1))=I_(avg(i))).

As discussed above, when in Region C, load estimator 44 measures thetime supply voltage V_(SUPPLY) takes to cross threshold voltages V₂ andV₃, and may use such measurement to update target average currentI_(avg). To illustrate, reference is made to FIG. 7 which depicts awaveform of supply voltage V_(SUPPLY) over a period of time and awaveform of an inductor current I_(L) (e.g., one of inductor currentsI_(L1), I_(L2), I_(L3)) over the same period of time. As shown in FIG. 7, load estimator 44 may measure a time Δt₁ it takes supply voltageV_(SUPPLY) to increase from threshold voltage V₂ to threshold voltageV₃. The change in voltage from threshold voltage V₂ to threshold voltageV₃ divided by the time Δt₁ may define a slope s₁. Similarly, loadestimator 44 may measure a time Δt₂ it takes supply voltage V_(SUPPLY)to decrease from threshold voltage V₃ to threshold voltage V₂. Thechange in voltage from threshold voltage V₃ to threshold voltage V₂divided by the time Δt₂ may define a slope s₂. Average inductor currentI_(avg(i)) through an individual power inductor 32 during a risingsupply voltage V_(SUPPLY) may be defined as a rise current I_(R), whileaverage inductor current I_(avg(i)) through an individual power inductor32 during a falling supply voltage V_(SUPPLY) may be defined as a fallcurrent I_(F).

Using a charge balance relationship for output capacitor 38 coupled tosupply voltage V_(SUPPLY), load estimator 44 may update target averagecurrent I_(avg) drawn from battery 22. For example, using themeasurement for rise current I_(R), target average current I_(avg) maybe updated in accordance with:

$I_{avg} = {I_{R} - {s_{1} \cdot \frac{C_{out}}{D_{i}^{\prime}}}}$

Where D′_(i) is equal to one minus the duty cycle of inductor currentI_(L) and C_(out) is a capacitance of output capacitor 38. The quotient

$\frac{C_{out}}{D_{i}^{\prime}}$may be unknown or uncertain, but may be estimated. For example, in someembodiments, load estimator 44 may estimate the quotient

$\frac{C_{out}}{D_{i}^{\prime}}$using fixed values. However, it an input voltage (e.g., voltageVDD_SENSE) is known, the inverse of D′_(i) may be approximately equal tothe quotient of supply voltage V_(SUPPLY) divided by such input voltage.Thus, the foregoing equation for updating target average current I_(avg)may be written:

$I_{avg} = {I_{R} - {s_{1} \cdot \frac{V_{SUPPLY}}{VDD\_ SENSE} \cdot C_{out}}}$However, such relationship may have uncertainty due to the approximationof output capacitance C_(out) and the assumption that boost converter 20is lossless. But, such uncertainty may be eliminated by using bothmeasurements for rise current I_(R) and fall current I_(F), as given bythe equation:

$I_{avg} = {I_{F} - {\frac{s_{2}}{s_{1} - s_{2}} \cdot \left( {I_{R} - I_{F}} \right)}}$If it is assumed that the increase in voltage from threshold voltage V₂to threshold voltage V₃ is equal in magnitude to the decrease in voltagefrom threshold voltage V₃ to threshold voltage V₂, then the foregoingequation for updating target average current I_(avg) may be written:

$I_{avg} = {\left( \frac{I_{R}}{\frac{\Delta t_{2}}{\Delta t_{1}} + 1} \right) + {\left( {1 - \frac{1}{\frac{\Delta t_{2}}{\Delta t_{1}} + 1}} \right)I_{F}}}$

The two approaches above for updating target average current I_(avg) mayeach have their own advantages and disadvantages. For example, theupdate based on one current measurement may be better at detectinglarge, fast transients, but could be inaccurate due to assumptionsregarding the duty cycle and output capacitance C_(out), and alsoassumes that changes in voltage and measurements of current are knownexactly. The update based on two current measurements may be more robustagainst offsets in the changes in voltage and measurements of current,but such approach assumes the load of power converter 20 is fixed overboth measurements, which may not be the case, especially in the presenceof large transients. Thus, in some embodiments, a hybrid approach may beused in which the single-measurement approach is used if only onemeasurement is available or if the single measurement is larger (orsmaller) than the dual measurement by more than the band of uncertaintyof the single-measurement approach, and the dual-measurement approach isused otherwise.

FIG. 8 illustrates a block diagram of selected components of an outerloop control subsystem 50 of current controller 46, in accordance withembodiments of the present disclosure. As shown in FIG. 8 , currentcontroller 46 may be implemented using logic inverters 52A and 52B,set-reset latches 54A and 54B, and multiplexers 56A and 56B.

Logic inverter 52A may invert comparison signal C₂ and set-reset latch54A may hysteretically generate control signal ENABLE such that controlsignal ENABLE is asserted when supply voltage V_(SUPPLY) falls belowthreshold voltage V₂ and is deasserted when supply voltage V_(SUPPLY)rises above threshold voltage V₄. When control signal ENABLE isdeasserted, control circuit 40 may disable charge switches 34 andrectification switches 36 and power converter 20 may be operated in theboost inactive mode.

Further, inverter 52B may invert comparison signal C₁ and set-resetlatch 54B may hysteretically generate control signal MAX_ENABLE thatindicates whether a maximum for target average current I_(avg) should begenerated by control circuit 40. Receipt of control signal RESET_MAX maydeassert control signal MAX_ENABLE, to return control of peak currentthreshold I_(pk) and valley current threshold I_(val) to the innercontrol loop. Multiplexer 56A may, based on control signal MAX_ENABLE, amaximum for peak current threshold I_(pk) and a target peak currentthreshold I_(pk) (e.g., derived from target average current I_(avg)calculated by load estimator 44), generate a peak current thresholdI_(pk). Similarly, multiplexer 56B may, based on control signalMAX_ENABLE, a maximum for valley current threshold I_(val), and a targetvalley current threshold I_(val) (e.g., derived from target averagecurrent I_(avg) calculated by load estimator 44), generate a valleycurrent threshold I_(val).

To further illustrate outer loop control by current controller 46,reference is made to FIG. 9 . As shown in FIG. 9 , in Region I of thewaveforms, supply voltage V_(SUPPLY) exceeds threshold voltage V₄, andboost converter 20 may be placed in the boost inactive mode as set-resetlatch 54A may cause control signal ENABLE to be deasserted, leavingboost converter 20 with a high-impedance. Accordingly, in Region I, theload of boost converter 20 may cause a decrease in supply voltageV_(SUPPLY).

When supply voltage V_(SUPPLY) decreases below threshold voltage V₂,set-reset latch 54A may cause control signal ENABLE to be asserted, andboost converter 20 may enter the boost active mode. In Region II of thewaveforms shown in FIG. 9 , load estimator 44 may in effect control peakcurrent threshold I_(pk) and valley current threshold I_(val), throughthe estimate of target average current I_(avg) performed by loadestimator 44. However, in the specific example shown in FIG. 9 , loadestimator 44 may not “turn around” supply voltage V_(SUPPLY) quickenough, and supply voltage V_(SUPPLY) may continue to decrease.

Accordingly, supply voltage V_(SUPPLY) may decrease below thresholdvoltage V₁, thus causing set-reset latch 54B to set, asserting controlsignal MAX_ENABLE, forcing peak current durrent I_(pk) and target valleycurrent I_(val) to their maximum values (maximum peak current I_(pk-max)and maximum valley current I_(avg-max)) in Region III of FIG. 9 . Aftersufficient increase in supply voltage V_(SUPPLY), set-reset latch 54Bmay reset and deassert control signal MAX_ENABLE, and load estimator 44may again regain control as shown in Region IV of the waveforms. Ifsupply voltage V_(SUPPLY) increases further again in excess of thresholdvoltage V₄, set-reset latch 54A may again deassert control signalENABLE, causing boost converter 20 to enter the boost inactive mode.

Accordingly, the outer loop implemented by current controller 46 maytoggle boost converter 20 between a maximum current and high-impedancestate, and bound a ripple in supply voltage V_(SUPPLY) to approximatelybetween threshold voltages V₁ and V₄ even when inner loop control ofload estimator 44 fails to regulate supply voltage V_(SUPPLY).

FIG. 10 illustrates a block diagram of selected components of an innercontrol loop subsystem 60 of current controller 46, in accordance withembodiments of the present disclosure. FIG. 11 illustrates examplewaveforms depicting examples of inner loop control for boost converter20, in accordance with embodiments of the present disclosure.

As shown in FIG. 10 , inner control loop subsystem 60 may receive targetaverage current I_(avg) calculated by load estimator 44, divide suchtarget average current I_(avg) by a number n of phase 24 present inboost converter 20, and apply each of a positive offset +Δ and anegative offset −Δ to target average current I_(avg)/n by offset blocks62A and 62B, respectively. The results of offset blocks 62A and 62B maybe respectively saturated to a minimum value by saturation blocks 64Aand 64B to generate rise current I_(R) and fall current I_(F),respectively. Adder blocks 68A and 68B may add one-half of ripplecurrent I_(ripple) to each of rise current I_(R) and fall current I_(F)and adder blocks 70A and 70B may subtract one-half of ripple currentI_(ripple) from each of rise current I_(R) and fall current I_(F). Basedon comparison signals C₂ and C₃, latch 66 may selectively assert anddeassert control signal TOGGLE to toggle selection of multiplexers 72Aand 72B to:

-   -   In the event control signal TOGGLE is asserted due to supply        voltage V_(SUPPLY) decreasing below threshold voltage V₂,        generate an intermediate peak current threshold I_(pk)′ and an        intermediate valley current threshold I_(val)′ such that        I_(pk)′=I_(R)+I_(ripple)/2 and I_(val)′=I_(R)−I_(ripple)/2, and        the mean inductor current is rise current I_(R).    -   In the event control signal TOGGLE is deasserted due to supply        voltage V_(SUPPLY) increasing above threshold voltage V₃,        generate intermediate peak current threshold I_(pk)′ and        intermediate valley current threshold I_(val)′ such that        I_(pk)′=I_(F)+I_(ripple)/2 and I_(val)′=I_(F)−I_(ripple)/2, and        the mean inductor current is fall current I_(F).

As shown in FIG. 8 above, intermediate peak current threshold I_(pk)′and intermediate valley current threshold I_(val)′ may be used by outerloop control subsystem 50 to generate peak current threshold I_(pk) andvalley current threshold I_(val).

Thus, toggling of control signal TOGGLE may maintain regulation ofV_(SUPPLY) between threshold voltage V₂ and threshold voltage V₃. Forexample, when control signal TOGGLE is high, the average per phasecurrent may be set to rise current I_(R). Because this value of currentis offset from target average current I_(avg) by positive offset +Δ, itmay cause supply voltage V_(SUPPLY) to rise. On the other hand, whencontrol signal TOGGLE is low, the average per phase current may be setto fall current I_(F). Because this value of current is offset fromtarget average current I_(avg) by negative offset −Δ, it may causesupply voltage V_(SUPPLY) to fall.

Occasionally, a change in loading at the output of power converter 20may lead to a change in target average current I_(avg), as shown at timeto in FIG. 11 , in which case load estimator 44 may modify targetaverage current I_(avg) as described above.

FIG. 12 illustrates example waveforms depicting examples of inner loopcontrol for boost converter 20 in light-load scenarios, in accordancewith embodiments of the present disclosure. For light-loads, targetaverage current I_(avg) calculated by load estimator 44 may be largerthan a minimum target average current I_(avg_min) applied by saturationsblocks 64A and 64B. Because rise current I_(R) and fall current I_(F)may be saturated in this scenario, inductor current I_(L) may be largerthan is required for steady-state operation of boost converter 20,forcing supply voltage V_(SUPPLY) to have a positive slope in Regions Iand III of FIG. 12 . When supply voltage V_(SUPPLY) crosses abovethreshold voltage V₄, set-reset latch 54A from outer loop controlsubsystem 50 may cause boost converter 20 to enter the boost inactiveregion, thus leading to forcing supply voltage V_(SUPPLY) to have anegative slope in Regions II and IV of FIG. 12 due to the high-impedancestate of boost converter 20. In light-load conditions, toggling betweenthe boost active state and the boost inactive state with fixedsaturation thresholds for peak current threshold I_(pk) and valleycurrent threshold I_(val) may maximize power efficiency.

In a simple implementation of control circuit 40, control circuit 40 maybe implemented as a digital control system that sets control parametersfor peak current threshold I_(pk), valley current threshold I_(val),control signal ENABLE, and the number n of phases 24 enabled. However,due to sample-and-hold circuitry that may be employed in such digitalimplementation and incumbent processing delays, several clock cycles ofdelay may occur between when comparators 42 toggle and when new controlparameters are determined. Such delay may contribute to overshoot andundershoot in supply voltage V_(SUPPLY) generated by power converter 20,which may lead to undesirable ripple and excessive voltage droop onsupply voltage V_(SUPPLY). It may be desirable to have a faster responseto quick load transients on supply voltage V_(SUPPLY) compared to thatwhich could be supported by a fully digital implementation of controlcircuit 40.

FIG. 13 illustrates a block diagram of selected components of controlcircuit 40A, in accordance with embodiments of the present disclosure.Control circuit 40A may be functionally and/or structurally similar inmany respects to control circuit 40 shown in FIG. 5 , with a maindifference being that current controller 46A is split into a digitalcalculation block 82 and an analog circuit 84. As described in greaterdetail below, analog circuit 84 may minimize delays that would bepresent in a fully-digital implementation by using pre-seeded values forcontrol parameters generated by digital calculation block 82 andselecting among such pre-seeded values by analog circuit 84 in order togenerate control parameters communicated to peak/valley controller 48and boost converter 20. Analog circuit 84 may by driven directly bycomparators 42, such that when comparators 42 toggle, analog circuit 84immediately changes state and chooses generated new control parametersfor peak current threshold I_(pk), valley current threshold I_(val),control signal ENABLE, and the number n of phases 24 enabled. Suchmanner of changing states and updating control parameters may create alow-latency path from comparators 42 to new, updated control parameters.On the other hand, digital calculation block 82 may be configured tocalculate the pre-seeded parameters based on the outputs of comparatorsand its internal control algorithm.

FIG. 14 illustrates a block diagram of selected components of an innercontrol loop subsystem 60A of current controller 46A, in accordance withembodiments of the present disclosure. Inner loop control subsystem 60Amay be functionally and/or structurally similar in many respects toinner loop control subsystem 60 shown in FIG. 10 , except thatmultiplexers 72A and 72B and a portion of analog state machine 80 may beimplemented by analog circuit 84, and other components of inner loopcontrol subsystem 60A may be implemented by digital calculation block82. As shown in FIG. 14 , digital calculation block 82 may generatepre-seeded values based on all comparison signals C₁, C₂, C₃, and C₄,and analog state machine 86 may be configured to, based on comparisonsignals C₂ and C₃, control selection of such pre-seeded values withmultiplexers 72A and 72B in order generate intermediate peak currentthreshold I_(pk) and intermediate valley current threshold I_(val)′.

FIG. 15 illustrates a block diagram of selected components of an outerloop control loop subsystem 50A of current controller 46A, in accordancewith embodiments of the present disclosure. Outer loop control subsystem50A may be functionally and/or structurally similar in many respects toouter loop control subsystem 50 shown in FIG. 8 , except thatmultiplexers 56A and 56B and a portion of analog state machine 86 may beimplemented by analog circuit 84. As shown in FIG. 15 , analog statemachine 86 may be configured to, based on comparison signal C₁ and acontrol signal RESET_MAX generated by digital calculation block 82,control between selection of pre-seeded values for maximum peak currentthreshold I_(pk_max) and maximum valley current threshold I_(val_max) onthe one hand and intermediate peak current threshold I_(pk)′ andintermediate valley current threshold I_(val)′ generated by innercontrol loop subsystem 60A on the other hand. Further, analog statemachine 86 may be configured to, based on comparison signals C₂ and C₄,control signal ENABLE for power converter 20.

In a boost converter 20 having multiple phases 24, all phases 24 may useidentical set points for peak current threshold I_(pk) and valleycurrent threshold I_(val), and a lookup table or other suitable approachmay be used to determine how many phases 24 are active based on targetaverage current I_(avg). Further, such lookup table or other suitableapproach may have hysteresis to prevent excessive enabling and disablingof an individual phase 24. In addition, the lookup table or anotherlookup table may be used to determine how many phases 24 are to beenabled in a maximum current state of power converter 20 (e.g., supplyvoltage V_(SUPPLY)<threshold voltage V₁).

Although the foregoing discussion contemplates current control andvoltage regulation of a boost converter 20, it is understood thatsimilar or identical approaches may be applied to other types ofinductor-based power converters, including without limitation buckconverters and buck-boost converters.

Referring back to FIGS. 3A-3C, each power inductor 32 of respectivephases 24 may draw a respective inductor current I_(L) (e.g., I_(L1),I_(L2), and I_(L3)). Also, because all phases 24 may use identical setpoints for peak current threshold I_(pk) and valley current thresholdI_(val) as described above, inductor currents I_(L1), I_(L2), and I_(L3)would all be expected to be in phase with one another in the event thatimpedances of each phase 24 were identical. However, in practicalimplementation, if impedances of each phase 24 are different but closein value, the respective inductor currents I_(L1), I_(L2), and I_(L3)may slowly drift in and out of phase with one another. But relativelylong periods may exist when two or more of respective inductor currentsI_(L1), I_(L2), and I_(L3) are in phase with one another.

FIG. 16 illustrates a block diagram of selected components of apeak/valley controller 48A, in accordance with embodiments of thepresent disclosure. In some embodiments, peak/valley controller 48A maybe used to implement peak/valley controller 48 shown in FIG. 5 . Asshown in FIG. 16 , peak/valley controller 48A may include comparators90A and 90B and latch 92. Comparator 90A may be configured to compare aninductor current I_(L) to valley current threshold I_(val), whilecomparator 90B may be configured to compare an inductor current I_(L) topeak current threshold I_(pk). Latch 92 (which may be implemented as aset-reset latch or other suitable circuit or logic device) may generatecontrol signals P_(x) (e.g., control signals P₁, P₂, P₃, etc.) and P_(x), (e.g., control signals P₁ , P₂ , P₃ , etc.) for controlling switchesof boost converter 20 as shown in FIG. 5 . For example, when inductorcurrent I_(L) falls below valley current threshold I_(val), latch 92 mayassert control signal P_(x) and deassert control signal P_(x) , and wheninductor current I_(L) falls below valley current threshold I_(val),latch 92 may deassert control signal P_(x) and assert control signalP_(x) .

FIGS. 17A-17C illustrate graphs of various example waveforms for batterycurrent I_(BAT), inductor currents I_(L1) and I_(L2), and controlsignals P₁ and P₂ versus time using peak/valley controller 48A, inaccordance with embodiments of the present disclosure. For purposes ofclarity and exposition, only two inductor currents I_(L1) and I_(L2) andtwo control signals P₁ and P₂ are shown in FIGS. 17A-17C, although boostconverter 20 may include more than two phases 24 with other inductorcurrents and control signals other than those shown in FIGS. 17A-17C. Asshown in FIGS. 17A-17B, when individual inductor currents I_(L1) andI_(L2) are in phase or nearly in phase with one another, a large ripple(e.g., equal to approximately two times the ripple current I_(ripple)present in a single inductor current I_(L)) may result on batterycurrent I_(BAT). If a number N of multiple phases 24 with in-phaseinductor current I_(L) are present, then the ripple on battery currentI_(BAT) may be N times the ripple current I_(ripple) present in a singleinductor current I_(L).

Such a ripple on battery current I_(BAT) may be problematic for numerousreasons, especially if the ripple is at a high frequency. For example,such ripple may result in decreased efficiency of boost converter 20,difficulty in sensing battery current I_(BAT), or may parasiticallycouple into surrounding circuity leading to electromagneticinterference. Further, such current ripple may appear on the inputvoltage to boost converter 20 and on supply voltage V_(SUPPLY),interfering with control of boost converter 20 by control circuit 40(e.g., interference with feedback control of control circuit 40dependent on the value of supply voltage V_(SUPPLY)).

To overcome problems associated with in-phase inductor currents I_(L),peak/valley controller 48A may be modified from that shown in FIG. 16 inorder to perform one or both of time-domain phase randomization orlevel-domain phase randomization, as described in greater detail below.

FIG. 18 illustrates a block diagram of selected components of an examplepeak/valley controller 48B with circuitry for performing time-domainphase randomization of inductor currents I_(L) in boost converter 20, inaccordance with embodiments of the present disclosure. In someembodiments, peak/valley controller 48B may be used to implementpeak/valley controller 48 shown in FIG. 5 . In addition, peak/valleycontroller 48B may be similar or identical in many respects topeak/valley controller 48A of FIG. 16 , with a main difference beingthat peak/valley controller 48B may include additional circuitryinterfaced between comparator 90A and the set input of latch 92 in orderto perform time-domain phase randomization with respect to comparison ofinductor current I_(L) to valley current threshold I_(val). As shown inFIG. 18 , the output of comparator 90A may be received by a tapped delayline 94 which may generate one or more outputs, each delaying the outputof comparator 90A by a respective delay amount. Further, a multiplexer96 may receive the un-delayed output of comparator 90A and the output(s)of delay line 94 and select one of such outputs based on a random numbern_(rand), such that the comparator signal received by the set input oflatch 92 is delayed by a random amount of time. As a result, as shown inFIG. 19 , random number n_(rand) may randomly delay the outputtransition of latch 92 from Q=0 to Q=1, which may delay transition froma transfer state of a phase 24 to a charging state of such phase 24, andthus also delay occurrence of a valley of an inductor current I_(L) insuch phase 24. As also shown in FIG. 19 , such delay may also result inrandomly delaying the output transition of latch 92 from Q=1 to Q=0,which may delay transition from the charging state of the phase 24 tothe transfer state of such phase 24, and thus also delay occurrence of apeak of an inductor current I_(L) in such phase 24. Such randomizationmay minimize phase alignment of individual inductor currents I_(L) inphases 24.

The additional circuitry used to provide time-domain phase randomization(e.g., delay line 94 and multiplexer 96) may be implemented to delay theresult of the comparison of inductor current I_(L) to valley currentthreshold I_(val) (e.g., as shown in FIG. 18 ), to delay the result ofthe comparison of inductor current I_(L) to peak current thresholdI_(pk), or both. This additional randomization circuitry may bereplicated for some or all of phases 24. In other words, in someembodiments, one or more phases 24 may each be controlled by arespective peak/valley controller 48A while one or more other phases 24may each be controlled by a respective peak/valley controller 48Bproviding time-domain randomization of inductor current I_(L) in somebut not all of phases 24; and in other embodiments, phases 24 may eachbe controlled by a respective peak/valley controller 48B providingtime-domain randomization of inductor current I_(L) in all of phases 24.

FIG. 20 illustrates a block diagram of selected components of an examplepeak/valley controller 48C with circuitry for performing level-domainphase randomization of inductor currents I_(L) in boost converter 20, inaccordance with embodiments of the present disclosure. In someembodiments, peak/valley controller 48C may be used to implementpeak/valley controller 48 shown in FIG. 5 . In addition, peak/valleycontroller 48C may be similar or identical in many respects topeak/valley controller 48A of FIG. 16 , with a main difference beingthat peak/valley controller 48C may include additional circuitryinterfaced in the path of valley current threshold I_(val) in order toperform level-domain phase randomization of one or more individualinductor currents I_(L). As shown in FIG. 20 , a multiplexer 98 mayreceive a plurality of level adjustments (e.g., −Δ, 0, +Δ, etc.) formodifying a level of valley current threshold I_(val) and select one ofsuch outputs based on a random number n_(rand). In turn, a combiner 99may combine such selected level adjustment with valley current thresholdI_(val) such that a modified valley current threshold I_(val) receivedby latch 92 includes a random level adjustment. As a result, as shown inFIG. 21 , random number n_(rand) may randomly delay (or advance) theoutput transition of latch 92 from Q=0 to Q=1, which may delaytransition from a transfer state of a phase 24 to a charging state ofsuch phase 24, and thus also delay occurrence of a valley of an inductorcurrent I_(L) in such phase 24. As also shown in FIG. 21 , such delaymay also result in randomly delaying the output transition of latch 92from Q=1 to Q=0, which may delay transition from the charging state ofthe phase 24 to the transfer state of such phase 24, and thus also delayoccurrence of a peak of an inductor current I_(L) in such phase 24. Suchrandomization may minimize phase alignment of individual inductorcurrents I_(L) in phases 24.

The additional circuitry used to provide level-domain phaserandomization (e.g., multiplexer 98 and combiner 99) may be implementedto apply a level adjustment to valley current threshold I_(val) (e.g.,as shown in FIG. 20 ), apply a level adjustment to peak currentthreshold I_(pk), or both. This additional randomization circuitry maybe replicated for some or all of phases 24. In other words, in someembodiments, one or more phases 24 may each be controlled by arespective peak/valley controller 48A while one or more other phases 24may each be controlled by a respective peak/valley controller 48Cproviding level-domain randomization of inductor current I_(L) in somebut not all of phases 24; and in other embodiments, phases 24 may eachbe controlled by a respective peak/valley controller 48C providingtime-domain randomization of inductor current I_(L) in all of phases 24.

The foregoing description may provide suitable regulation of supplyvoltage V_(SUPPLY) in many instances. However, in the event of a largeincrease in load current I_(LOAD) drawn from boost converter 20, supplyvoltage V_(SUPPLY) may droop excessively below threshold voltage V₁, asshown in FIG. 22 . FIG. 22 illustrates a large step change in loadcurrent I_(LOAD) at a time t₁. At a later time t₂, supply voltageV_(SUPPLY) may fall below threshold voltage V₁, which may cause controlcircuit 40 to enable additional phases 24 of boost converter 20 (e.g.,increase the number of enabled phases 24 from one to more than one).When such additional phases 24 are enabled, they may begin in theirindividual charging states. In the charging state, inductor currentsI_(L) of the newly-enabled phases 24 may increase, but no current may betransferred from such phases to load current I_(LOAD) during thecharging state, so supply voltage V_(SUPPLY) may decrease. Eachnewly-enabled phase 24 may remain in its charging state until theirinductor currents I_(L) reach target peak current I_(pk). Thus, thelonger each newly-enabled phase 24 takes to reach target peak currentI_(pk), the more supply voltage V_(SUPPLY) may droop. The rate ofcurrent increase for inductor currents I_(L) may be given by:

$\frac{{dI}_{L}}{dt} = \frac{VDD\_ SENSE}{L}$where L is the inductance of a power inductor 32. Notably, due tointernal impedances of battery 22, resistance of sense resistor 28, andparasitic impedances of electrical traces between battery 22 and boostconverter 20, sense voltage VDD_SENSE may decrease from battery voltageV_(BAT) as battery current I_(BAT) increases, in accordance with Ohm'slaw.

FIG. 22 illustrates supply voltage V_(SUPPLY) and inductor currentsI_(L) of newly-enabled phases 24 under two scenarios: (i) a scenariolabeled by label “A” on waveforms wherein sense voltage VDD_SENSE isrelatively high; and (ii) a scenario labeled by label “B” on waveformswherein sense voltage VDD_SENSE is relatively low. In scenario A, thetime of the charging state of the newly-enabled phases 24 may be shortdue to the higher sense voltage VDD_SENSE, while in scenario B, the timeof the charging state of the newly-enabled phases 24 may be longer dueto the lower sense voltage VDD_SENSE.

To overcome this problem, control circuit 40 or another component ofboost converter 20 or power delivery system 1 may selectively increasevoltage thresholds V₁, V₂, V₃, and V₄ when sense voltage VDD_SENSE isdeemed to be sufficiently low (e.g., below a threshold sense voltageV_(THRESH)), as shown in FIG. 23 . As shown in FIG. 23 , in response tosense voltage VDD_SENSE decreasing below threshold sense voltageV_(THRESH), control circuit 40 may cause voltage thresholds V₁, V₂, V₃,and V₄ to increase by the same amount (e.g., in a controlled, rampedmanner as shown in FIG. 23 ), as shown at point A in FIG. 23 .Accordingly, if a large step in load current I_(LOAD) occurs at point Bshown in FIG. 23 while sense voltage VDD_SENSE is low, supply voltageV_(SUPPLY) my droop, but because voltage thresholds V₁ and V₂ have beenraised, such droop may be minimal, to point C shown in FIG. 23 . Whenand if sense voltage VDD_SENSE again increases above threshold sensevoltage V_(THRESH) (at point D shown in FIG. 23 ) or if boost converter20 enters its bypass mode, control circuit 40 may cause voltagethresholds V₁, V₂, V₃, and V₄ to decrease to their original levels(e.g., in a controlled, ramped manner as shown in FIG. 23 ). A Booleanflag RAISE_V_(x)_FLAG is shown in FIG. 23 , which may indicate a stateof voltage thresholds V₁, V₂, V₃, and V₄ (e.g., RAISE_V_(x)_FLAG=0 indefault state, RAISE_V_(x)_FLAG=1 when voltage thresholds V₁, V₂, V₃,and V₄ are increased).

Using the technique illustrated in FIG. 23 , an absolute droop of supplyvoltage V_(SUPPLY) may be minimized, but the amount of time boostconverter 20 spends in its bypass mode is not impacted, therebypreserving efficiency.

To prevent frequent toggling of voltage thresholds V₁, V₂, V₃, and V₄ inresponse to a sense voltage VDD_SENSE near threshold sense voltageV_(THRESH), control circuit 40 may include hysteretic control to performthe technique illustrated in FIG. 23 . For example, FIG. 24 illustratesselected components of a control subsystem 100 (e.g., which may beimplemented in whole or part by control circuit 40) providing forvoltage-domain hysteretic control of threshold voltages V₁, V₂, V₃, andV₄, in accordance with embodiments of the present disclosure. As shownin FIG. 24 , a comparator 102 may compare sense voltage VDD_SENSE tothreshold sense voltage V_(THRESH) and the result of such comparison maybe received by set input of set-reset latch 108, causing flagRAISE_V_(x)_FLAG to be asserted when sense voltage VDD_SENSE decreasesbelow threshold sense voltage V_(THRESH), as shown in FIG. 25 . Further,a comparator 104 may compare sense voltage VDD_SENSE to higher thresholdsense voltage V_(THRESH-HI) and the result of such comparison may belogically OR'ed by OR gate 106 with an indication of whether boostconverter 20 is in its bypass mode. The output of OR gate 106 may bereceived by reset input of set-reset latch 108, causing flagRAISE_V_(x)_FLAG to be deserted when sense voltage VDD_SENSE increasesbelow higher threshold sense voltage V_(THRESH-HI), or if boostconverter 20 enters its bypass mode, as shown in FIG. 25 . In turn, flagRAISE_V_(x)_FLAG may be received by a select input of a multiplexer 110,which may select an amount (e.g., 0 or ΔV) to add to each of thresholdvoltages V₁, V₂, V₃, and V₄ based on the value of flag RAISE_V_(x)_FLAG.Accordingly, when sense voltage VDD_SENSE increases above higherthreshold sense voltage V_(THRESH-HI), threshold voltages V₁, V₂, V₃,and V₄ may be decreased to their default values V₁′, V₂′, V₃′ and V₄′,and when sense voltage VDD_SENSE decreases below threshold sense voltageV_(THRESH), threshold voltages V₁, V₂, V₃, and V₄ may be increased toV₁′+ΔV, V₂′+ΔV, V₃′+ΔV, and V₄′+ΔV, respectively.

For purposes of clarity and exposition, components (e.g., filters, rampgenerators, etc.) for causing ramping of threshold voltages V₁, V₂, V₃,and V₄ (e.g., as shown in FIG. 23 ) are not depicted in FIG. 24 , butmay nonetheless be present in control subsystem 100.

As another example, FIG. 26 illustrates selected components of a controlsubsystem 120 (e.g., which may be implemented in whole or part bycontrol circuit 40) providing for time-domain hysteretic control ofthreshold voltages V₁, V₂, V₃, and V₄, in accordance with embodiments ofthe present disclosure. As shown in FIG. 26 , a comparator 122 maycompare sense voltage VDD_SENSE to threshold sense voltage V_(THRESH)and the result of such comparison may be received by an input of aninstant-set, delayed-release timer 124, causing flag RAISE_V_(x)_FLAG tobe asserted when sense voltage VDD_SENSE decreases below threshold sensevoltage V_(THRESH), as shown in FIG. 27 . Timer 124 may then hold flagRAISE_V_(x)_FLAG to be asserted until sense voltage VDD_SENSE increasesabove threshold sense voltage V_(THRESH) for a programmed minimumduration of time. For example, period A shown in FIG. 27 may be shorterthan the programmed minimum duration of time, so the increase of sensevoltage VDD_SENSE above threshold sense voltage V_(THRESH) for period Amay be insufficient for timer 124 to deassert flag RAISE_V_(x)_FLAG.However, period B shown in FIG. 27 may be equal to the programmedminimum duration of time, so the increase of sense voltage VDD_SENSEabove threshold sense voltage V_(THRESH) for period B may be sufficientfor timer 124 to deassert flag RAISE_V_(x)_FLAG. Further, should boostconverter 20 enter its bypass mode, timer 124 may reset and causedeassertion of flag RAISE_V_(x)_FLAG. In turn, flag RAISE_V_(x)_FLAG maybe received by a select input of a multiplexer 130, which may select anamount (e.g., 0 or ΔV) to add to each of threshold voltages V₁, V₂, V₃,and V₄ based on the value of flag RAISE_V_(x)_FLAG. Accordingly, whensense voltage VDD_SENSE decreases below threshold sense voltageV_(THRESH), threshold voltages V₁, V₂, V₃, and V₄ may be increased toV₁′+ΔV, V₂′+ΔV, V₃′+ΔV, and V₄′+ΔV, respectively, decreasing to defaultvalues V₁′, V₂′, V₃′, and V₄′ in response to boost converter 20 enteringits bypass mode or in response to sense voltage VDD_SENSE increasingabove threshold sense voltage V_(THRESH) for the programmed minimumduration of time.

For purposes of clarity and exposition, components (e.g., filters, rampgenerators, etc.) for causing ramping of threshold voltages V₁, V₂, V₃,and V₄ (e.g., as shown in FIG. 23 ) are not depicted in FIG. 26 , butmay nonetheless be present in control subsystem 120.

As another example, FIG. 28 illustrates selected components of a controlsubsystem 140 (e.g., which may be implemented in whole or part bycontrol circuit 40) providing for control of threshold voltages V₁, V₂,V₃, and V₄, in accordance with embodiments of the present disclosure. Asshown in FIG. 28 , a comparator 142 may compare sense voltage VDD_SENSEto threshold sense voltage V_(THRESH) and the result of such comparisonmay be received by a first input of a logical AND gate 146. In addition,a comparator 144 may compare supply voltage V_(SUPPLY) to thresholdvoltage V₃ and the result of such comparison may be received by a secondinput of logical AND gate 146. Accordingly, logical AND gate 146 maytrigger the set input of a set-reset latch 147 such that set-reset latch147 asserts flag RAISE_V_(x)_FLAG when VDD_SENSE<V_(THRESH) andV_(SUPPLY)>V₃, as shown in FIG. 29 . In addition, the output ofcomparator 142 may be inverted by logical inverter 149 and trigger thereset input of set-reset latch 147 such that flag RAISE_V_(x)_FLAG isdeasserted when VDD_SENSE>V_(THRESH).

In turn, flag RAISE_V_(x)_FLAG may be received by a select input of amultiplexer 150, which may select an amount (e.g., 0 or ΔV) to add toeach of threshold voltages V₁, V₂, V₃, and V₄ based on the value of flagRAISE_V_(x)_FLAG. Accordingly, when VDD_SENSE<V_(THRESH) andV_(SUPPLY)>V₃, threshold voltages V₁, V₂, V₃, and V₄ may be increased toV₁′+ΔV, V₂′+ΔV, V₃′+ΔV, and V₄′+ΔV, respectively, and may be decreasedto their default values V₁′, V₂′, V₃′, and V₄′ otherwise.

The advantage of waiting is that it may minimize a risk of supplyvoltage V_(SUPPLY) drooping below threshold voltages V₁ and V₂ asthreshold voltages V₁, V₂, V₃, and V₄ are increased. To illustrate, ifsupply voltage V_(SUPPLY) is below threshold voltage V₂, control circuit40 may rapidly increase load current I_(LOAD) delivered by boostconverter 20. Further, if supply voltage V_(SUPPLY) is below thresholdvoltage V₁, control circuit 40 may set load current I_(LOAD) to itsmaximum. Either of these events may cause undesirable disturbances andspikes on battery current I_(BAT). However, the control implemented bycontrol subsystem 140 may reduce or eliminate such disadvantages.

For purposes of clarity and exposition, components (e.g., filters, rampgenerators, etc.) for causing ramping of threshold voltages V₁, V₂, V₃,and V₄ (e.g., as shown in FIG. 23 ) are not depicted in FIG. 28 , butmay nonetheless be present in control subsystem 140.

In some embodiments, control circuit 40 may implement one of controlsubsystem 100, control subsystem 120, and control subsystem 140 tocontrol threshold voltages V₁, V₂, V₃, and V₄. In other embodiments,control circuit 40 may combine two or more of control subsystem 100,control subsystem 120, and control subsystem 140 in any suitablecombination to control threshold voltages V₁, V₂, V₃, and V₄.

As noted above, a large increase in load current I_(LOAD) drawn fromboost converter 20 may lead to a droop in supply voltage V_(SUPPLY).FIG. 30 illustrates a graph of various example waveforms showing varyingdegrees of droop for supply voltage V_(SUPPLY) in response to a step inload current I_(LOAD) and also depicts inductor currents I_(L) forphases 24 of boost converter 20, in accordance with embodiments of thepresent disclosure. As previously noted, when such a droop occurs,supply voltage V_(SUPPLY) may fall below threshold voltage V₁, which maycause control circuit 40 to enable additional phases 24 of boostconverter 20 (e.g., increase the number of enabled phases 24 from one tomore than one). When such additional phases 24 are enabled, they maybegin in their individual charging states. In the charging state,inductor currents I_(L) of the newly-enabled phases 24 may increase, butno current may be transferred from such phases to load current I_(LOAD)during the charging state, so supply voltage V_(SUPPLY) may decrease.Each newly-enabled phase 24 may remain in its charging state until theirinductor currents I_(L) reach target peak current I_(pk). Thus, thelonger each newly-enabled phase 24 takes to reach target peak currentI_(pk), the more supply voltage V_(SUPPLY) may droop. As also notedabove, the rate of current increase for inductor currents I_(L) may begiven by:

$\frac{{dI}_{L}}{dt} = \frac{VDD\_ SENSE}{L}$

FIG. 30 depicts three possible scenarios for settings of target peakcurrent I_(pk) for phases 24. In a first case, target peak currentI_(pk) may be at a value I_(pk-lo) at which inductor current I_(L) of anewly-enabled phase 24 reaches target peak current I_(pk) quickly andthus begins supplying current to the load of boost converter 20 quickly.However, target peak current value I_(pk-lo) may be insufficient toovercome the droop in supply voltage V_(SUPPLY), which may have acharacteristic shown by waveform V_(SUPPLY-LO).

In a second case, target peak current I_(pk) may be at an optimum valueI_(pk-opt), which may represent a minimum value for target peak currentI_(pk) sufficient to support the load. In this case, inductor currentI_(L) of newly-enabled phase(s) 24 may reach target peak current I_(pk)quickly and also be sufficient to support the load, allowing supplyvoltage V_(SUPPLY), which may have a characteristic shown by waveformV_(SUPPLY-OPT), to efficiently overcome the droop.

In a third case, target peak current I_(pk) may be at a value I_(pk-hi)at which inductor current I_(L) of newly-enabled phase(s) 24 reachestarget peak current I_(pk) slowly and thus begins supplying current tothe load of boost converter 20 slowly. Thus, while target peak currentvalue I_(pk-hi) may be sufficient to overcome the droop in supplyvoltage V_(SUPPLY) (which may have a characteristic shown by waveformV_(SUPPLY-HI)) over time, an excessive amount of droop may occur upuntil the time at which time newly-enabled phase(s) 24 begins deliveringcurrent.

Accordingly, it may be desirable to use the optimum value I_(pk-opt)which is large enough to support a given maximum load current I_(LOAD),while small enough to minimize the duration of the charging state ofnewly-added phase(s) 24 and thus minimize the magnitude of droop insupply voltage V_(SUPPLY). However, such optimum value may change overtime depending on a state of boost converter 20 and a power deliverysystem in which boost converter 20 is present. Accordingly, choosingsuch optimum value I_(pk-opt) may prove challenging.

To generate an optimum value for target peak current I_(pk) (as well asvalley peak current I_(val)), control circuit 40 (or a componentthereof, such as load estimator 44 or current controller 46) may settarget average current I_(avg) based on sense voltage VDD_SENSE. Toillustrate, given a known maximum power draw P_(MAX) from the output ofboost converter 20, an instantaneous target average current I_(avg-max)for power draw P_(MAX) may be given as:

$I_{{avg} - \max} = {\frac{P_{MAX}}{{VDD\_ SENSE}(t)}\frac{1}{n}}$where n is an approximation of a power efficiency of boost converter 20.Maximum target peak current I_(pk-max) and maximum target valley currentI_(val-max) may be calculated as follows:

${I_{{pk} - \max} = {I_{{avg} - \max} + \frac{I_{ripple}}{2}}}{I_{{val} - {{ma}x}} = {I_{{avg} - \max} - \frac{I_{ripple}}{2}}}$

These values for maximum target peak current I_(pk-max) and maximumvalley current I_(val-max) may be used as illustrated in FIGS. 8 and 15and as described above for calculating target peak current I_(pk) andvalley current I_(val). FIG. 31 illustrates a graph of various examplewaveforms for supply voltage V_(SUPPLY) generated by boost converter 20,inductor currents I_(L) for newly-enabled phase(s) 24, and sense voltageVDD_SENSE in accordance with embodiments of the present disclosure. Inparticular, FIG. 31 depicts control by control circuit 40 to varymaximum target peak current I_(pk-max) as a function of sense voltageVDD_SENSE. In FIG. 31 , supply voltage V_(SUPPLY) may fall belowthreshold voltage V₁ at point A, which may trigger control circuit 40 toenable one or more additional phases 24. Further, the decrease of supplyvoltage V_(SUPPLY) to below threshold voltage V₁ may cause controlcircuit 40 to set target peak current I_(pk) to maximum target peakcurrent I_(pk-max) (and set target valley current I_(val) to maximumtarget valley current I_(pk-val)). Further, as sense voltage VDD_SENSEdecreases, maximum target peak current I_(pk-max) (and maximum targetvalley current I_(pk-val)) may increase as a function of sense voltageVDD_SENSE. Accordingly, boost converter 20 may take advantage of a lowerinitial peak current requirement shown at point B in FIG. 31 so thatboost converter 20 may begin transferring current to its output sooner,thereby preventing excessive droop on supply voltage V_(SUPPLY). Maximumtarget peak current I_(pk-max) (and maximum target valley currentI_(pk-val)) may increase to steady-state levels, shown at point C inFIG. 31 .

As used herein, when two or more elements are referred to as “coupled”to one another, such term indicates that such two or more elements arein electronic communication or mechanical communication, as applicable,whether connected indirectly or directly, with or without interveningelements.

This disclosure encompasses all changes, substitutions, variations,alterations, and modifications to the example embodiments herein that aperson having ordinary skill in the art would comprehend. Similarly,where appropriate, the appended claims encompass all changes,substitutions, variations, alterations, and modifications to the exampleembodiments herein that a person having ordinary skill in the art wouldcomprehend. Moreover, reference in the appended claims to an apparatusor system or a component of an apparatus or system being adapted to,arranged to, capable of, configured to, enabled to, operable to, oroperative to perform a particular function encompasses that apparatus,system, or component, whether or not it or that particular function isactivated, turned on, or unlocked, as long as that apparatus, system, orcomponent is so adapted, arranged, capable, configured, enabled,operable, or operative. Accordingly, modifications, additions, oromissions may be made to the systems, apparatuses, and methods describedherein without departing from the scope of the disclosure. For example,the components of the systems and apparatuses may be integrated orseparated. Moreover, the operations of the systems and apparatusesdisclosed herein may be performed by more, fewer, or other componentsand the methods described may include more, fewer, or other steps.Additionally, steps may be performed in any suitable order. As used inthis document, “each” refers to each member of a set or each member of asubset of a set.

Although exemplary embodiments are illustrated in the figures anddescribed below, the principles of the present disclosure may beimplemented using any number of techniques, whether currently known ornot. The present disclosure should in no way be limited to the exemplaryimplementations and techniques illustrated in the drawings and describedabove.

Unless otherwise specifically noted, articles depicted in the drawingsare not necessarily drawn to scale.

All examples and conditional language recited herein are intended forpedagogical objects to aid the reader in understanding the disclosureand the concepts contributed by the inventor to furthering the art, andare construed as being without limitation to such specifically recitedexamples and conditions. Although embodiments of the present disclosurehave been described in detail, it should be understood that variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the disclosure.

Although specific advantages have been enumerated above, variousembodiments may include some, none, or all of the enumerated advantages.Additionally, other technical advantages may become readily apparent toone of ordinary skill in the art after review of the foregoing figuresand description.

To aid the Patent Office and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants wishto note that they do not intend any of the appended claims or claimelements to invoke 35 U.S.C. § 112(f) unless the words “means for” or“step for” are explicitly used in the particular claim.

What is claimed is:
 1. A method of randomizing inductor current in atleast one of a plurality of parallel coupled peak/valleycurrent-controlled power converters, wherein each plurality of parallelcoupled peak/valley current-controlled power converters comprises arespective phase of a multi-phase power converter, the methodcomprising: randomly selecting an offset current parameter; adding theoffset current parameter to a reference current parameter to generate amodified reference current parameter; and comparing the inductor currentto the modified reference current parameter to control the inductorcurrent during one or both of a charging state and a transfer state ofthe at least one of the plurality of parallel coupled peak/valleycurrent-controlled power converters; wherein the randomly selecting,adding, and comparing steps are applied to one or more but less than allof the respective phases of the multi-phase power converter.
 2. Themethod of claim 1, wherein the reference current parameter is a targetvalley current for the inductor current.
 3. The method of claim 1,wherein the reference current parameter is a target peak current for theinductor current.
 4. A system of randomizing inductor current in atleast one of a plurality of parallel coupled peak/valleycurrent-controlled power converters, wherein each plurality of parallelcoupled peak/valley current-controlled power converters comprises arespective phase of a multi-phase power converter, the systemcomprising: selection logic configured to randomly select an offsetcurrent parameter; a combiner configured to add the offset currentparameter to a reference current parameter to generate a modifiedreference current parameter; and a comparator configured to compare theinductor current to the modified reference current parameter to controlthe inductor current during one or both of a charging state and atransfer state of the at least one of the plurality of parallel coupledpeak/valley current-controlled power converters; wherein the randomlyselecting, adding, and comparing steps are applied to one or more butless than all of the respective phases of the multi-phase powerconverter.
 5. The system of claim 4, wherein the reference currentparameter is a target valley current for the inductor current.
 6. Thesystem of claim 4, wherein the reference current parameter is a targetpeak current for the inductor current.